1. Field of the Invention (Technical Field).
The invention relates specifically to a simplified and subsequently improved method to produce an oil free scroll type vacuum pump which is capable of achieving vacuum pressures below 1 torr through the application of the invention's dynamic orbital vacuum seal between the opposing scroll halves in order to prevent atmospheric pressure from entering into the pump.
2. Background Art
Scroll type vacuum pumps are pumps that consist of two plate halves which have involute archimedes spiral walls formed into each plate half. The plates are placed together with the spirals interleaved. An orbiting motion is employed to either or both plates in order to trap a volume of gas from the outside diameter of the scroll spiral walls and then compress the gas along the spiral walls in a crescent shaped chamber that becomes smaller until the gas is expelled to atmosphere at the outlet port located at the center of the spiral walls. In order to achieve vacuum pressure less than 1 torr, it has previously been necessary to seal the orbiting outside diameter mating joint between the two scroll halves with a large diameter bellows. This bellows is welded to each scroll half in a configuration that can accommodate the required orbital travel and prevent atmospheric pressure from entering the pump. Another method locates one or both scroll plates, along with the components that convert the rotary drive to the required orbital motion, inside the vacuum space. Both of these designs are more expensive to produce than the invention's improved scroll vacuum pump which utilizes the invention's dynamic orbital vacuum seal to seal the orbiting outside diameter mating joint between the scroll halves. This expense has limited the application of scroll technology in the vacuum industry to special applications.